Fine pattern lithography using a helium field ion source

Despite the many reports on characteristics of hydrogen field ion (FI) sources, there have been only a few reports on focusing experiments. We developed a stable helium FI source and a focusing column with a gimbal assembly for beam axis alignment, and carried out focusing experiments. Scanning ion microscope images of a Au wire were observed using the focusing column. From the image resolution, the ion probe diameter was estimated to be ∼200 nm. We exposed a 260-nm-thick polymethylmethacrylate resist on a Si substrate, which produced 200-nm-wide lines. A 70-nm-wide space was also formed. The proximity effect was negligible even if the space between the lines was 100 nm. Thus, we confirmed that a helium FI source is suitable for fine pattern lithography.